Electrokinetic properties of conidia of Acremonium diospyri

Abstract Microelectrophoretic analysis of conidia of lactose grown cultures of Acremonium diospyri revealed a predominantly amino carboxyl surface, possibly associated with polyphosphate. Glucosegrown conidia possessed a much lower overall charge density. These observations are discussed in relation to the general cultural behaviour of A. diospyri in the presence of these different carbon sources.     

Patterns of airborne conidia of Stemphylium vesicarium, the causal agent of brown spot disease of pears, in relation to weather conditions

Seven-day volumetric spore samplers were installed in pear orchards of northern Italy, in the years between 1993 and 2002, and operated continuously during the development of brown spot epidemics (mid-April–mid-August), caused by Stemphylium vesicarium. Aerial concentration of conidia was recorded at 2 h intervals to study their diurnal and seasonal patterns and the influence of weather conditions. The diurnal periodicity of aerial conidia showed a peak around midday and low counts in the dark. The increase in spore concentration was significantly correlated with the reduction of relative humidity and wetness in early morning, and the increase of wind in late morning and afternoon. Conidia of S. vesicarium became easily airborne to form a regular component of the air-spora in pear orchards, while ascospores were caught only sporadically. Differences between years concerned total spore counts and numbers of peaks (defined as days with more than 30 conidia/m³ air per day). Periods with highest spore counts occurred in late-May to early-June (in 2 years), mid to end of June (5 years), or after mid-July (3 years). There was a significant correlation between spore peaks and days with favourable weather conditions, defined as days with air temperature between 15 and 25°C and high humidity, particularly a wet period longer than 10 h. Occurrence of one or more consecutive days with favourable weather conditions determined an increase in the airborne concentration of conidia, which usually lasted some days and then decreased.     

Comparison of two methods for estimation of spray deposits after application of microbial pesticides

The effectiveness of two methods for the determination of deposition of mycopesticides on hemlock trees by spray application was compared. One method employs water and oil sensitive paper cards; the other uses a combination of two adhesive tapes (scotch tape) with different adhesive properties. Two fungi, Beauveria bassiana and Lecanicillium muscarium, and three fungal formulations based on whey, oil, and whey together with oil were used to evaluate the efficacy of the two methods. The new method has shown the certain advantages in comparison with the traditional method which is based on the sensitive paper cards. Generally, number of droplets counted was greater in the case of adhesive tape utilization. These observations were noted for the two entomopathogenic fungi. However, different results were noted for the three different types of fungal formulations. The presence of conidia was observed in all three formulations using adhesive tape. The number of conidia localized on hemlock twigs was affected by fungal formulation. The adhesive tape method allowed counting more droplets than the sensitive cards. Other advantages of the adhesive tape method include the ability to observe the outer appearance and internal structure of the droplets and to count fungal propagules directly on the leaf surfaces.     

Light-Induced Lipid Peroxidation in Isolated Chloroplasts and Role of α-Tocopherol

Lipid peroxidation in isolated chloroplasts illuminated by visible light and the role of α-tocopherol in chloroplasts were studied. The TBA reactants and fluorescent products derived from lipid peroxidation were formed by illumination. Peroxidation was inhibited by free radical scavengers and ¹O₂ quenchers. Hydroxy methyl octadecanoates, which were the reduced and hydrogenated products of lipid hydroperoxides, were detected. Among them, 10-and 15-hydroxy methyl octadecanoates were generated from ¹O₂ oxidation. On the other hand, lipid hydroperoxides did not accumulate in this peroxidation process. The amount of α-tocopherol in the chloroplasts decreased with lipid peroxidation, and α-tocopheryl quinone was produced. The results indicate that α-tocopherol acts as a free radical scavenger for photo-oxidation of chloroplasts.     

Spectral filters for the control of Botrytis cinerea

Experiments performed in vitro examined the sporulation of Botrytis cinerea (grey mould) under different spectral distributions. Eighty‐three isolates, taken from plants of primula (Primula vulgaris) at different locations throughout the UK, were incubated in the dark, with visible light only and visible plus near‐ultraviolet (nUV) light. On average, compared to isolates not exposed to nUV, sporulation was increased 54‐fold following illumination with nUV light. No isolates showed complete insensitivity to near ultraviolet. New polyethylene materials with different optical properties were then tested on two typical isolates. A film which removed nUV up to 405 nm, compared to a film with nUV absorption up to 384 nm, resulted in the lowest production of conidia (by 5‐fold). The former film was used to clad horticultural polyethylene tunnels in which crops of P. vulgaris and strawberry were grown for two seasons and the incidence of B. cinerea assessed throughout the growth of the crops. The incidence of infection on the P. vulgaris and strawberries was reduced by c. 50% and c. 26% respectively with the nUV blocking film compared to a standard film. The results are discussed in terms of the potential of spectral filters as a novel means of grey mould control in greenhouse‐produced crops.     

Rice recycling: a simple strategy to improve conidia production in solid-state cultures

Here we studied at a laboratory scale a potential strategy to revalorize the residual rice remaining at the end of a conventional conidia production process in solid-state culture. The conidia production of Trichoderma asperellum Th-T4 (3) and Metarhizium robertsii Xoch-8.1 started with the use of fresh rice (unrecycled rice) as the substrate (cycle one), and continued with the use of recycled rice in successive cycles of conidia production. The rice remaining at the end of the first cycle was reused without any further sterilization or reinoculation. As a result, it was observed that the conidia production and productivity significantly increased in both fungi. Conidia production in T. asperellum Th-T4 (3) increased from 1 × 10⁹ (first cycle) to 2·9 × 10⁹ conidia per gram of initial dry substrate (con⋅gds⁻¹) (second cycle using recycled rice), while in M. robertsii Xoch-8.1, this parameter increased form 5·7 × 10⁸ to 1·4 × 10⁹ con⋅gds⁻¹. Both fungi grew faster and conidiated earlier when recycled rice was used as the substrate, therefore, conidia productivity was also significantly improved. Furthermore, the use of recycled rice did not affect conidia viability. This is the first report about a recycling methodology completely free of extra-processing steps, and useful to increase conidia production and productivity.